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Unit 7: The Energy in Chemical Reactions—Thermodynamics and Enthalpy

Glossary

Bomb calorimeter
A device used to measure the change in internal energy (ΔU) of a system at constant volume.
Bond enthalpy
The amount of enthalpy (or energy) needed to break one mole of a certain chemical bond.
Caloric
A precursor to the modern understanding of heat. Caloric was believed to be an invisible fluid capable of carrying heat.
Calorie
A unit of energy equal to the amount of energy needed to raise 1 gram of water by 1 degree Celsius.
Calorimeter
A device used to measure either the change in the internal energy or the change in enthalpy of a system.
Chemical energy
The energy of a system due to the arrangement and bonding of atoms.
Diesel engine
An internal-combustion engine in which the compression of fuel, not a spark plug, causes the fuel to ignite.
Electrical work
The work done on a charged particle by an electric field.
Endothermic
Absorbing heat from the surroundings.
Enthalpy
The amount of heat absorbed or released during a reaction or process under constant pressure.
Exothermic
Releasing heat to the surroundings.
Fire piston
A fire-starting device that burns tinder by rapidly compressing a gas.
First Law of Thermodynamics
Energy can never be created or destroyed. The total energy in the universe is constant.
Heat
The transfer of thermal energy between a system and its surroundings.
Heat of fusion
The amount of heat needed to melt one mole of a substance.
Heat of vaporization
The amount of heat needed to boil one mole of a substance.
Hess's Law
The change in enthalpy of a reaction (ΔH) is the same if the reaction happens in a single step or in a series of steps. Thus, the series of steps must have individual enthalpy changes that add up to the total change in enthalpy for the process
Internal energy
The sum total of all different types of energy in a system (thermal, chemical, etc.).
Joule
The International System of Units (SI) unit of energy, equal to one newton-meter.
Kinetic energy
The energy of an object due to its motion.
Potential energy
The energy of an object due to its position.
Pressure-volume work
Work done on or by a system due to compression or expansion of gases.
Surroundings
The area outside the boundaries of the system being studied.
System
The part of the universe being studied.
Thermal energy
The energy in a system that relates to the temperature of the system.
Thermochemistry
The study of energy in chemical reactions.
Velocity
The rate of change of the position of an object.
Vis viva
Latin for "living force." Vis viva was the precursor to the modern concept of kinetic energy.
Work
The way a system exchanges energy with the surroundings, excluding heat transfers (pressure-volume work, electrical work, etc.).

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